Modified pectins have long been recognized as being useful in suppressing the metastasis of cancer cells. This effect is thought to be due to binding of the modified pectin to galectins, in particular galectin-3, and possibly to other as-yet unidentified saccharide-binding cell surface receptors. Several compositions of modified pectins have been described. See Platt et al. “Modulation of Lung Colonization of B16-F1 Melanoma Cells by Citrus Pectin” J. Natl. Cancer Inst. 84(6):438-442 (1992); Inohara et al. “Effects of Natural Complex Carbohydrate (citrus pectin) on Murine Melanoma Cell Properties Related to Galectin-3 function” Glycoconjugate J. 11:527-532 (1994); Pienta et al. “Inhibition of spontaneous metastasis in a Rat Prostate Cancer Model by Oral Administration of Modified Citrus Pectin” J. Natl. Cancer Inst. 87:348-353 (1995); U.S. patent application Ser. Nos. 08/024,487, 08/819,356, 2003/0013682, 2003/0004132, and 2002/0107222, and U.S. Pat. Nos. 6,423,314, 5,681,923, 5,834,442, and 5,895,784. The disclosures of each of these applications and patents are incorporated herein by reference in their entirety. Synthetic carbohydrate derivatives have also been reported to bind to and block galectin-3. See PCT application WO 02/057284.
Examples of modified pectins of the type described previously are described by formulas I-IV below:

In the above representations, n is an integer greater than 1, Xn-1 represents a short side-chain of neutral sugar residues, Galp is galactose, Rhap is rhamnose, GalpA is galacturonic acid and Araf is arabinose. X can be any of several sugars found in pectin side chains, including but not limited to β-Apif, β-Rhap, α-Fucp, β-GlcpA, α-GalpA, β-GalpA, β-DhapA, Kdop, β-Acef, α-Galp, and α-Arap.
The existing methods used to prepare modified pectins generally suffer from poorly controlled chemical processes and difficult product isolation and purification processes. These factors either separately or combined typically result in widely varying therapeutic activities, molecular weights, polydispersities, concentrations, monosaccharide compositions, linkage makeup, potency and impurity profiles. Many of these processes employ organic solvents, which can create explosion hazards and toxicological effects from residual solvent and require expensive disposal of solvent waste.